Mining machine bits



Oct. 2, 1956 c. T. MOEHLMANN MINING MACHINE BITS Filed Sept. 25, 1953 FIGZ.

FIGI.

FIGS.

INVENTOR; CARL T. MOEHLMANN,

ATTORNEYS MINING MACHINE BITS Carl T. Moehlmann, University City, Mo., assignor to Central Mine Equipment Company, St. Louis, Mo., a corporation of Missouri Application September 25, 1953, Serial No. 382,341

8 Claims. (Cl. 262-33) This invention relates to mining bits, and more particularly, to kerf-cutting machine bits.

An inexpensive bit of this type is made from bar stock rolled to a diamond or elliptical cross section, the bar being sliced obliquely to form opposed outwardly-tapering cutting faces. Such bits ofier certain advantages, but the cutting point is necessarily widened as it wears away, with the result that the load on the machine tends to vary over the useful life of a set of bits.

In other words, there is a gradual grinding down of the tapering point, so that the kerf cut thereby gradually widens. Consequently, an operator heretofore was presented with the choice of ineflicient bit utilization (frequent replacement of the bits prior to full use thereof), or of perhaps operating his machine inefliciently.

It is also an object of the invention to reduce the amount of dust generated at the face of the mine.

It is accordingly an object of the present invention to provide an improved bit that can be made inexpensively and used reversibly in existing holders, but which does not have the disadvantages mentioned above. Briefly, this objective is achieved by forming the bit with cuttingface portions of uniform, rather than narrowing, Width and by providing a central head or rib-forming section of greater thickness. This bead, which may be of rounded, triangular or rectangular cross-sectional shape, strengthens the bit and permits use of the bit in the holders of existing machines. The bit is cut from bar stock as before, but the cross-sectional shape of the stock necessarily includes fiat side walls extending parallel to one another from a centrally-disposed rib.

Other features of the invention will be in part apparent from and in part pointed out in the following detail description taken in connection with the accompanying drawings, in which:

Fig. 1 is a front elevation of an improved bit of this invention;

Fig. 2 is a side elevation of the bit shown in Fig. 1;

Fig. 3 is a view similar to that of Fig. 1, illustrating an alternative embodiment of the invention;

Fig. 4 is a view similar to that of Fig. 1, showing a third embodiment of the invention;

Fig. 5 is a view similar to that of Fig. 1, illustrating an additional embodiment of the invention;

Fig. 6 is a view like that of Fig. 1, but shows a further modification; and

Fig. 7 is an oblique View of a bit holder illustrating a bit of the Fig. 1 type mounted therein.

It will be understood that in an undercutter mining machine, the cutting operation is performed by tooth-like bits which are mounted in a chain. A popular type of bit is made from bar stock of diamond or elliptical cross section, the bar being sliced at an angle of thirty degrees with respect to its axis and with five-eighths of an inch between slices. The parallel faces formed by the angled cuts produce a rhornbic shape, wherein the faces are offset from one another so that the bit may be reversed. When mounted in the holder, one face seats against the rates Patent holder and a portion of the other face projects outwardly as a digging or cutting point. This tapering portion is necessarily subjected to a grinding operation, hence is worn away over a period of use. After the tip is worn down to the holder, the bit is reversed and subsequently replaced.

I have discovered that a change of the cutting face from a tapering to a non-tapering shape results in a bit that develops less dust at the mine face and more uniform load on the machine, Without loss of the advantages of this type of bit. This is explained by the observation that the cutting edge at the tip does not change from a relatively small or sharp curve to an increasingly larger and blunter shape when the cutting face does not taper.

Referring now to the drawings, the bit is shown to have fiat parallel faces 1 and 3, which are offset from one another, as in previous bits. Also, the top and bottom portions 5 and 7 thereof are rounded and lie at an angle of approximately thirty degrees with respect to the faces 1 and 3. In contrast to prior constructions, however, the faces are of a non-tapering shape. In manufacture, the bit is cut from bar stock having flat web sections 9 and 11 of uniform width extending from opposite sides of a central bead section 13 of substantially greater thickness. As a result, the side edges of the cutting faces indicated at A and B, respectively, extend parallel but for the rounded extremities.

In Figs. 1 and 2, the bead 13 is shown to be of semicircular shape, but other shapes may also be used. For example, Fig. 3 shows a bead 113 of rectangular outline; Fig. 4 shows a bead 213 of triangular outline; Fig. 5 shows a bead 313 of slightly bulging outline; and Fig. 6 shows a double-bead arrangement 413.

In connection with Fig. 2, in particular, it will be noted that the length of the cutting face A between the upper tip (junction of lines 1 and 5) and the beginning of the rib is less than the length of the top edge 5, the same relationship holding true with the opposite face B. The rib 13 extends parallel to the edges 5 and 7 in inwardly spaced relationship therefrom. Finally, the center of the rib section at one cutting face is generally opposite the top edge of the other cutting face. In other words, the portion of the rib at face 1 is opposite the junction of lines 5 and 3 of Fig. 2. If the bit were considered reversed so that the cutting face B was etfective, the rib portion at face 3 is generally opposite the junction of lines 1 and 7.

Referring to Fig. 7, this type of bit may be fitted within a conventional bit holder generally designated 15. Such holders usually are formed with a bit-receiving pocket or support face 17 of rhornbic outline in order to accommodate the rhombic-type bits used heretofore. It will be apparent that the beaded construction herein disclosed cooperates with such bit-receiving pockets.

In contrast to previous bits of the rhombic shape, however, the shape of the cutting edge present at the tip does not change as the tip is ground off during use. The grinding action at the tip tends to maintain the corners rounded so that the only change is in the length of the cutting face of the bit with no change in the width of the cutting tip. The gradual reduction in length has no material affect upon the width of the cut or kerf, hence the bit may be used until the tip is worn down to a point that would expose the end of the holder, without the adverse effects developed when rhombic bits are so used. The bit is readily reversible and replaceable in the same manner as prior bits, and the thick central portion provides strength against breakage.

Having thus described the invention, what is claimed and desired to be secured by Letter Patent is:

1. A mining machine bit having opposed generally parallel reversible cutting faces oflset from one another,

said bit having fiat parallel side walls, and a rib projecting from at least one side of the bit and lying at an oblique angle with respect to said cutting faces, said rib being set back from the cutting ends of the cutting faces.

2. A mining machine bit as set forth in claim 1, wherein said rib is of a generally rounded shape in cross section.

3. A mining machine bit as set forth in claim 1, wherein said rib is of a generally rectangular shape in cross section.

4. A mining machine bit as set forth in claim 1, wherein said rib is of a generally triangular shape in cross section.

5. A mining machine bit as set forth in claim 1 wherein ribs project from both sides of the bit.

6. A mining machine bit having web sections with top and bottom edges extending parallel to one another, cutting faces extending across the bit between said top and bottom edges at an oblique angle with respect thereto, a bead portion extending parallel to said top and bottom edges between said cutting faces, said head section being spaced inwardly from said top and bottom edges, each of said web sections having flat parallel side walls and said head section being of a width substantially greater than that of said web section.

7. A bit as set forth in claim 6, wherein the length of the cutting face between the cutting point and the rib is less than the length of the adjacent top edge.

8. A mining bit as set forth in claim 6, wherein the center of the rib section at one cutting face is generally opposite the top edge of the other cutting face.

References Cited in the file of this patent UNITED STATES PATENTS 1,435,309 Kenton Nov. 14, 1922 1,679,135 Holmes July 31, 1928 1,685,196 Gilbert Sept. 25, 1928 2,217,348 Bowman Oct. 8, 1940 2,415,107 Morrow Feb. 4, 1947 

